Method of introducing halogens into electric lamps

ABSTRACT

In the process of introducing a halogen into a lamp in the form of a halogenated hydrocarbon, the feed conduit or exhaust tube is extended into the interior of the lamp bulb where it contains a tungsten surface area which is locally heated to a temperature sufficiently high to decompose the hydrocarbon and precipitate the carbon thereat.

United States Patent lnventor Oskar Herrmann Berlin, Germany Appl. No. 864,719 Filed Oct. 8, 1969 Patented Nov. 9, 1971 Assignee Patent-Treuhand-Gesellschaft fur elektrische Gluhlampen mbH Priority Nov. 21, 1968 Germany P l8 10 149.0

METHOD OF INTRODUCING HALOGENS INTO ELECTRTC LAMPS 2 Claims, 2 Drawing Figs.

int. C1 110lj 9/38 Field of Search 316/24, 30

[56] References Cited UNlTED STATES PATENTS 278,417 5/1883 Edison 316/24 411,019 9/1889 Edison 316/30 438,298 10/1890 Edison 316/24 1,874,537 8/1932 Jaycox... 316/24X 1,955,780 4/1934 Warnkem" 316/24 X 2,829,941 4/1958 Laubscher... 316/30 3,221,197 11/1965 Coppola 316/24 X Primary ExaminerJohn F. Campbell Assirmn! Elraminer-Richard Bernard Lazarus Almrneys-0tto Tichy, Henry P. Truesdell, Frank L.

Neuhauser, Oscar B. Waddell and Joseph B. Forman ABSTRACT: In the process of introducing a halogen into a lamp in the form of a halogenated hydrocarbon, the feed conduit or exhaust tube is extended into the interior of the lamp bulb where it contains a tungsten surface area which is locally heated to a temperature sufiiciently high to decompose the hydrocarbon and precipitate the carbon thereat.

PATENTEDuuv 9 I97! lnven tor Oskav Herrmann by 0x5 His A t tofl neg METHOD OF INTRODUCING HALOGENS INTO ELECTRIC LAMPS Application Ser. No. 812,629, filed Apr. 2, 1969 by Theo Berlinghof and assigned to the same assignee as the present case, discloses a method of manufacturing incandescent lamps with an addition of gaseous halogens to the fill gas, introduced by thermal decomposition of a dosed or measured quantity of a halogenated hydrocarbon such as dibromomethane or methyl iodide added to the fill gas, wherein the thermal decomposition of the halogenated hydrocarbon added to the fill gas is effected prior to introduction in the lamp envelope by localized heating of a section of the feed conduit in front of the tipoff spot of the lamp to a temperature above the decomposition temperature of the halogenated hydrocarbon. Preferably, decomposition of the usually used dibromomethane takes place in the exhaust tube attached to the lamp envelope which after filling of the lamps is tipped off during sealing and is thereby removed.

Said method proved to be extremely successful when used in the manufacture of incandescent halogen lamps of relatively small bulb volume. The volume of incandescent halogen lamps of this kind comprising an envelope of quartz glass or of a similar refractory, light-transmissive material is generally only a few cubic centimeters. With incandescent halogen lamps comprising an envelope of hard glass and, consequently, a considerably larger volume, more particularly for lamps of higher wattages such as, for example, or kw. (kilowatts), it was found that decomposition of the halogenated hydrocarbon in the exhaust tube, now necessarily larger in diameter, and with the heating-up temperature lower in the case of hard glass then in the case of quartz glass, did not always take place in sufficient amounts and, consequently, carbon deposits might occur in the lamp bulb by decomposition of the residual halogenated hydrocarbons in places which adversely affect the light emission of the lamp.

The present invention eliminates said drawbacks; it constitutes a further improvement of the process of manufacture of incandescent halogen lamps disclosed in the aforesaid application ofBerlinghof.

In accordance with the invention, the method of manufacture of incandescent lamps comprising an addition of gaseous halogens to the fill gas, introduced by thermal decomposition of a dosed quantity of a halogenated hydrocarbon such as dibromomethane or methyl iodide added to the fill gas by limited local heating of a section of the feed conduit to a temperature above the decomposition temperature of the halogenated hydrocarbon, is characterized in that decomposition of the halogenated hydrocarbon added to the fill gas is effected in the exhaust tube within the lamp bulb, for which purpose heated tungsten members are disposed in the exhaust tube on which elemental carbon, when flowing therethrough, deposits, which carbon is liberated by decomposition of the halogenated hydrocarbon. Consequently, a tube section of tungsten may be provided in the exhaust tube with a filling of tungsten chips or grit which is heated by an electrically heated auxiliary filament, the auxiliary filament being so rated as to burn out when the finished incandescent lamp is put in operation at its intended normal operating voltage. The tube section of tungsten may however also be heated to the requisite temperature for decomposition of the halogenated hydrocarbon by means of an energy source arranged outside the lamp bulb such as, for example, a directional thermal radiator or a highfrequency field. Furthermore, an electrically heated tungsten filament disposed in the exhaust tube proved suitable, the filament being rated in respect of its electrical characteristics so that it burns out when the finished incandescent lamp is put in operation at its normal intended operating voltage. Said tungsten filament may likewise be wound in bifilar manner or as an inverted coil.

The process according to the invention is further described in connection with the accompanying drawing wherein:

FIG. 1 is an elevation, partly in section, of a hard-glass incandescent halogen lamp, and

FIG. 2 is a fragmentary similar view of the neck portion and the exhaust tube of a modification.

FIG. 1 shows an incandescent halogen lamp rated for a wattage of 10 kw. at an operating voltage of 220 volts. The lamp bulb l is of hard glass, i.e., a glass having a transformation point above 700 C. such as, for example, an alumino-silicate glass. The bulb has a diameter of about 180 mm. and a height of 320 mm. The planar filament 2 is disposed within the mount between the support bridges 3 and 4 so that in operation a luminous area of about 50 mm. by 35 mm. is formed. Five and 6 denote the sealed lead-in wires. Seven is the exhaust tube with tube section 8 of tungsten. Said tube section incorporates tungsten chips or grit 9 which are secured to the inner surface of said tube section. The auxiliary filament 10 of, for example, thin tungsten wire surrounds said structure. It is connected with the lead-in wires 5 and 6 and is so dimensioned that it begins to glow at a voltage below the lamp operating voltage, for example, at 100 volts. The interior of the lamp bulb is connected via the exhaust tube 7 with the exhaust and gas fill device (not shown).

FIG. 2 shows the neck portion of a similar hard-glass incandescent halogen lamp with the exhaust tube 7 and the sealed lead-in wires 5 and 6. A tungsten filament 10a is disposed in the exhaust tube. The tungsten filament is connected to the lead-in wires 5 and 6. It begins to glow at a voltage below the lamp operating voltage, for example, at volta and, ac cordingly, attains a temperature sufficiently high for decomposition of the halogenated hydrocarbon flowing therethrough. The tungsten filament may also be wound in bifilar manner or as an inverted coil.

After the conventional pretreatment for purification of the components contained in the lamp bulb, the halogen-containing gas filling is introduced in the lamp. At this time, the prepared mixture of fill gas and halogenated hydrocarbon, for example, nitrogen with 0.3 to 1 percent of dibromomethane, fiows through the exhaust tube 7 into the lamp bulb. The tungsten tube 8 with the tungsten chips 9 incorporated therein is heated by auxiliary filament 10 so that the elemental carbon resulting from decomposition of the dibromomethane while flowing therethrough, deposits in this place. In the embodiment illustrated in FIG. 2, the elemental carbon is deposited on the tungsten filament 10a.

The mixture now formed of fill gas and bromine, or hydrogen bromide, respectively, fills the lamp bulb. Subsequent to introduction of the filling, the lamp is closed in known manner by tipping off and sealing the exhaust tube. Immediately thereafter, the intended operating voltage of 220 volts is applied to the lamp, and the auxiliary filament 10 or the tungsten filament 10a burns out. The sudden overheating may cause a portion of the deposited carbon or of carbon compounds such as tungsten carbide, to evaporate and to precipitate by settling in objectionable places on the inner wall surface of the lamp bulb. In order to reliably prevent this, the interior of the lamp may additionally be provided with a baffle plate which is adapted to deflect the vapors so that precipitation is thereby effected in a zone or area where light emission is not impaired.

lclaim:

1. In the method of manufacture of incandescent lamps comprising an addition of gaseous halogens to the fill gas, introduced by thermal decomposition of a dosed quantity of a halogenated hydrocarbon added to the fill gas and wherein a localized area of the feed conduit into the interior lamp bulb is heated to a temperature above the decomposition temperature of the halogenated hydrocarbon, said decomposition of the halogenated hydrocarbon takes place within said feed conduit by providing a tube section of tungsten disposed in said extension of the feed conduit, said tube section containing tungsten particles electrically heated by an auxiliary filament which is so rated that it burns out when the finished lamp is operated at its normal rated voltage and carbon from the decomposition of said halogenated hydrocarbon is deposited upon said tungsten particles.

duit by providing an auxiliary tungsten filament disposed in said extension of the feed conduit, said tungsten filament being electrically heated and so rated that it burns out when the finished lamp is operated at its normal rated voltage and carbon from the decomposition of said halogenated hydrocarbon is deposited upon said tungsten filament. 

2. In the method of manufacture of incandescent lamps comprising an addition of gaseous halogens to the fill gas introduced by thermal decomposition of a dosed quantity of a halogenated hydrocarbon added to the fill gas and wherein a localized area of the feed conduit into the interior lamp bulb is heated to a temperature above the decomposition temperature of the halogenated hydrocarbon, said decomposition of the halogenated hydrocarbon takes place within said feed conduit by providing an auxiliary tungsten filament disposed in said extension of the feed conduit, said tungsten filament being electrically heated and so rated that it burns out when the finished lamp is operated at its normal rated voltage and carbon from the decomposition of said halogenated hydrocarbon is deposited upon said tungsten filament. 